Originally Posted by A9X-308
Yes. Get a test signal source with test tones at 0dBFS, play it through the AVR and use a multimeter to measure the voltage at the sub out on the AVR, output of the MD and the power amp output (speaker terminals). The latter you do by getting the 8R power, say 400W, multiply by 8 and square root the result. This gives you the RMS voltage 56.56Vrms which is the maximum for your amp.
With the proper reference source and the AVR MVL = '0' and the SW output @ '0', there's no way anyone measured 12V from any Onkyo receiver.
Once you've balanced the output of SW jack with the input sensitivity of the Mini, you then have to face the reality of the power supply being used with the Mini. Boost can easily clip PS rails depending on the PS circuit being used and the amount of boost needed (preferred).
Once that's settled and the output of the Mini is not clipping the input of your amplifier, the amps gains must be set for the incoming signal and the speakers being driven by the amp.
I use actual scenes from movies for a worse-case signal out of the signal shaper (Mini, DCX, or whatever), after the AVR SW jack. The hottest scenes were from HTTYD, WOTW. With the Onk AVR set to MVL = '0' and the SW trim also at '0' and my analog SEQSS set to +10dB Boost, the highest reading was just under 10V. I then set the gain range for the amplifier (an all-new, modded 14K "clone"), used the AVR SW trim to calibrate SW level (which required lowering the SW trim to -3dB) and I use the amps gain attenuator knob to run the subs hot if and when...
No clips, no runs, no errors.
Plug and play is likely never to succeed.